Process of making sulfuric anhydrid.



-UNITED STATES reruns cusses.

N Drawing.

\ CARLETON ELLIS, 0F MQNTCLAIR, NEW JERSEY, A-SSIG-NGR T0 ELLIS-FGSTEE CGEI'EAHY,

A CORPORATION' OF NEW JERSEY PROCESS 033' MAKING SULE'URIG ANHYDEIB.

To all whom it may concern;

Be it known that l, GARLnroN ELLIS, a citizen of the United States, residing at Montclai'r, in the county of Essex and State of New Jersey, have invented certain new. and. useful Improvements in Processes of Making Sulfuric Anhyclrid, of which thefollowing is a specification.

This invention relates 'to a process for making sulfuric anhydricl and particularly fuming sulfuric acid or oleum, involving the oxidation of sulfur dioxicl with oxygen or air to sulfur trioxicl and relates especially to the use of certain compouucls of certainheavy metals with chromic acid or cromium material as will be more particularly here1nfiter'descrlbcd and claimecl. v

The standard catalytic material for the manufacture of sulfur trioxicl by the contact process is platinum and not infrequently this material is difhcult to secure in large quantities and also is very costly. Furthermore, it is very easily affected by arsenic and other bodies acting as catalyzer poisons. In the present invention a relatively cheap material is used as a catalytic agent and this material normally is of a character not so readily ail'ected by arsenic and the like so that expense in operatiohlis saved, While the initial cost of the catalytic material is low as compared with the cost of platinum heretofore generally used.

In its preferred embodiment my catalyzcr consists of or includes compounds of the nature of chromate of tin and specifically stem- 'nic chromete or compounds of stannic' tin With chromium oxicl, or other heavy metals andacidic radicals of an analogous character may likewise be used in place of the fore- 1 going or in conjunction therewith.

'The-catalyzer may be prepared by dissolv ing ten parts of ammonium bichi'omete in water and carefully neutralizing with dilute ammonia water uhtil a solution is obtained which is no longer acid to litmus. Fifty "parts of Washed asbestos or other voluminous carrier are thoroughly impregnated lwith this solution and the mixture then either with or without drying, treated with a solution containing ten parts of stannic chlorid. This mixture is evaporated to dryness with constant stirring and ignited, until fumes of ammonium chlorid cease to be evolved. The catalyzer may also be prepared by Specification of Letters Yatent.

timony, lead, bismuth, caclm -riel as for instance the use c a cerrier or the method of purification er n'ecipitetion of the tin chromate may some other met-lino. plo "fl In the preparation of en catalyzer, l preferably do not employ salts chromic acid with the fixed ullielis, since a pre ence of even it smell emouut of alkali in the finished catelyzer appears to considerably lower its catalytic efficiency, fol the o-Xiclation'oi sulfur elioxid to triosiil.

I call attention. also, to the fact that the proportions shove given correspond sub stantially to chemically equivalent proportions oi: tin amlchromium compounds but in many instances l have employed. various other )roportions,-With good results, ad l have a so employed other metal such as ann. and the like (metals Whose oxicls "capable of absorbing relatively large ameimts of sulful clioxicl) in :lacc of t'mfi The catalyzer prep-areal as shove, may be "used by passing; sulfur (liosid and oxygen,

or containing these, through or in contact with a bed of the catalyst, ata tempera ture of about 800-950$ R, a good Working range being 8504906" F, and in scmecases substantially combining proportions, Without a considerable excess oil free oxygen has heretofore'heen generally employed.

As source oi sulfur (liOXld, pyrite burner gases may be employed or sulfur clioxiol obtained from the lmrning oi sulfur. In any case, the gases should be freed as far as possible from dust so as not to clog the catalyzer chamber With dust particles but the absolute removal of arsenic and similar poisons is not required. This makes possi' lilo the application of the presentprocess to the oxidation of sulfur dioxicl 1n smelter smoke or fume Without the employment of Patented. May 2%, 391*? Application Elici- Ilune 13, 1518. 56118.1 Flo. 103,5fifi.

we ttecl, or

the sulfur dioxitl and oxygenmay approach such expensive purification apparatus,there- It is preferable to have the gases fairly dry before entering the contact chamber and in any event more uniform results are obtained by maintaining the moisture content uniform.

While with platinum as the catalytic ma-. terial' it is preferable not to exceed eight per cent. or so of sulfur dioxid in the gas mixture with the present catalyzer good results can be obtained employing even as high as twelve per cent. of sulfur dioXid thereby reducing the amount of heat required to bring the gas mixture to the requisite temperature. On the other hand the present process may be carried out with a gas mixture containing 2 or 3% and upward.

Using a mixture containing 8 per cent. of sulfur dioxid admixed with air at a temperature of approximately 800 F., conversion to sulfur trio'xid is eighty two to eighty four per cent. and by absorbing the sulfuric anhydrid so produced. and passing the residual gases through a second mass of catalyzer the conversion is renderednnore complete so that a total conversion of ninety two to ninety six per cent. is possible. Using about 6% of the dioxid, a conversion of 88-93% or thereabout been obtained in long continued tests, by only one passage through the catalytic mass.

The heat of the sulfur burners may be employed in the heating operationsrequired, as

' for example, in heating the gases after the fit) first absorption with sulfuric acid so as to bring the temperature up to a point where they can be introduced into the second catalyzer chamber under good working cond.i tions.

In using this catalyze any of the standard forms of apparatus adapted for such catalytic treatment may be employed. The

double absorption method set forth. above enables a satisfactory degree of conversion to be obtained. If desired, any residual sulfur dioxid may be absorbed in alkali to form sulfite or bisulfite.

Var ous combinations may be made with the chromium catalyzer and other catalyzers, also with the chromium. catalyzer and other catalyzei's in any desired sequence, in the case of the double absorption method. For example pyrite cinder may be the catalyzer in the first treatment and tin chromate in the second treatment, or vice The extending material, asbestos or the like may be omitted if desired, and the catalyzer may be made up into the form of porous blocks, plates or granules, or other suitable form.

lVhile I have described in this specification the use of the tin compounds and o'xy compounds of chromium in proportions different from those necessary to form tin chr0- mate, I call attention to the fact that the use of these materials in such other proportions is not claimed herein, but is claimed in my co-pending application Serial Numbers 65,285 and 75,028, and. catalysts of the general character-herein described are not claimed in the present application, but are claimed in my copending application Serial #723,028 and in a joint application filed by myself and H. M. Weber, Serial Number (57,357.

This application is in part a continuation of my prior application #37,!43 filed June 30, 1915, paragraphs 1, 2, 3, l, 5, 6, 10, 11,

12, 13, 14-, 15 and 16 (after the preamble) 'dioXid is converted. to sulfuric anhydrid.

'8. The process of making sulfuric anhydrid which comprises passing gases containing sulfur dioxid and oxygen into contact with a catalyzer comprising tin chromatef 4. The process of making sulfuric acid. which comprises exposing a. gaseous current containing sulfur dioxid and oxygen to' the action of tin chromate at a temperature at which said cliromate acts as a catalyst, in passing the products of reaction through sulfuric acid to absorb sulfuric anhydrid, in aassing the residual gases through a secon mass of tin chromate material in removing; the sulfuric anhydrid formed in the residual gases.

'5. The process of making sulfuric anhyd-rid which comprises passing a mixture tin and chromium, capable of acting as a catalyzer, said compound being substantially free from fixed alkali compounds.

8. A process ramm rs containing sulfur dioxid and oxygengainto contact with a catalyzer capa bleof 'causi'ngia partial combination thereing g 7. The process of making sulfuric anhydrid which comprisespassing gases containing surfur dioxid and-oxygen intoc'ontact with a catalytic compound containing tin and Chromium, without previous removal whereby sulfuric anhydrid isformed.

which comprises passing a of, removing at least the major part of the so formed sulfur trioxiqlyand passing the remaining gases in contact with a second catalyzer capable of converting a further portion of said gas mixture; at least one of said catalyzers containing tin and chromium in substantially combining proportions.

9. A process which comprises passing gases containing suifur dioxid and oxygen in contact with a catalyzer mass comprischromium and a metal Whose oxid is capable ofabsorbing sulfur dioxid, both the chromium and the other metal being in an oxidized condition, and these being present in substantially combinin proportions, said catalyzer being substantia ly free from fixed alkali compounds.

10. The process whichcomprises passing pyrites burner gases, without purification from arsenical impurities in contact with a catalyst comprising a compound containing tin and chromium in substantially combining proportions.

ed by the 11. "A process which comprises passing pyrites burner gases in contactw chromate catalyzer, said catalyzer being free fromjgltraces of compounds of the' fixed alkalis;

12. A process which comprises bringing a gas mixture containing sulfur dioxid and oxygen into contact with a catalyst comprising voluminous chromium oxid, Without previous puri fication of said gas mixture from arsenical compounds. I

13. A process which comprises bringing a gas mixture comprising sulfur dioXid and oxygenyin about the proportions representformula 2SO +O into contact with a catalyst comprising voluminous flaky of making sulfur trioxid agtm oxid of chromium, without previous re moval of arsenical impurities from said.

mixture.

14. A process which comprises bringing S0 and 0 into contact with a catalyst comprising chromium oxid and a heavy metal oxid capable of absorbing S0 Without previous removal said gas. r

15. In the manufacture of sulfuric anhy drid which comprises passing a gas mixof arsenical impurities from ture comprising sulfur dioxid and oxygen over a catalyzer comprising tin and chromium in an oxidized state, while at a temperature of about 800 to 950 F.

In testimony whereof I aflix my signature.

GARLETON ELLIS, 

